The present invention relates to die casting machinery and specifically hot chamber die casting machinery.
Hot chamber die casting machines generally include a hot chamber or pot in which the material which is to be used in the casting process is contained. This material, which is kept in the molten state, is automatically drawn into a die charging device which is at least partially submerged within the molten metal. Thus, there is not ladling of molten material to the die as with certain other casting processes. The automatic charging is, of course, most advantageous; however, certain limitations are placed on the charging mechanism.
Conventional charging mechanisms generally employ a plunger operating through a vertical cylinder. To direct the casting material to the die from the vertical cylinder, a gooseneck is employed which conveys the material to a position above the level of the molten supply and outwardly over the rim of the pot to the die location. The vertical orientation of the charging cylinder ensures that the driving mechanism is located above the pot so that the plunger may be easily pulled without requiring a first draining of the pot and sealing problems are minimized.
In spite of the advantages associated with the vertical arrangement, certain inherent difficulties also exist. The gooseneck required with a vertically arranged cylinder exhibits a substantial pressure loss with the casting material being forced at sufficient speed to reach all portions of the die quickly. The orientation of the charging cylinder also requires that the gooseneck extend over a substantial distance. This results in a cooling of the charged material prior to its reaching the die if some form of additional heating is not provided. To overcome the cooling problem, the gooseneck does not extend to the die. Instead, a nozzle is provided to span a substantial distance between the gooseneck and the die. The nozzle is then kept warm by means of torches directed at the nozzle. This arrangement better maintains the material at the appropriate temperature but results in the very rapid erosion of the nozzle.
The location of the vertical plunger above the pot which cooperates with the vertical charging cylinder also exhibits an inherent disadvantage in that this mechanism tends to interfere with proper access to the pot of molten material for replenishing the pot and the like. Practical experience has shown that the process required with most conventional systems for replenishing the pot has resulted in the improper removal of the pot covers by workers who are not exercising reasonable care for their own safety. Removal of these covers provides added convenience for the workers in replenishing the pot. However, adding solid material to the molten reservoir can result in splashing and the like which could possibly endanger the worker. Consequently, conventional systems, albeit safe, can be used improperly and thereby endanger the irresponsible worker.